Bests & Worsts Reviews from Amazon

I worked for the National Weather Service and the US Navy. Accurate hygrometers are expensive. Most cheap hygrometers are inaccurate and cannot be calibrated. This one is an exception. I liked it enough to purchase a second unit. But be aware that, like all hygrometers, it needs to be re-calibrated every couple of years. Calibration, using nothing more than salt, water, and a clear, enclosed container (75% humidity) is easy. You can find info online describing details of the procedure. I use more water and salt than most sources recommend---as long it has the consistency of wet sand. I suggest waiting at least 12 hrs for the humidity in the bag or chamber to stabilize at 75%. Calibration of the thermometer is more challenging unless you have a laboratory grade, liquid-in-glass thermometer (most consumer thermometers--digital or otherwise--are unreliable).